Аннотация
This review summarizes recent domestic and international advances in salt-tolerant surfactants for enhanced oil recovery, with emphasis on surfactant types, interfacial tension behavior, phase behavior, and engineering applications. With the increasing demand for the development of high-salinity and high-temperature (HSHT) reservoirs, surfactant flooding systems are facing increasingly stringent requirements in terms of thermal stability, salt-tolerance under complex brine conditions, and controllability of interfacial and microemulsion phase behavior. This review focuses on surfactants for salt-tolerant and temperature-resistant microemulsion systems, emphasizing the evolution of molecular structures and their roles in regulating microemulsion phase behavior under HSHT conditions. First, the limitations of conventional anionic, nonionic, and cationic surfactants commonly used in enhanced oil recovery are summarized, highlighting their pronounced sensitivity to high-salinity conditions (especially in the presence of divalent ions) and elevated temperatures, which often result in interfacial tension rebound, phase range window shrinkage, and reduced system stability. Second, structural modification strategies based on the incorporation of highly hydrophilic or salt-tolerant functional groups—such as sulfonate, amide, and extended poly (pothylene oxide and ethylene) (PO and EO) groups—are explored, with particular attention to their effectiveness in improving solubility, suppressing salting-out, and broadening the middle-phase region at moderate-to-high salinity. Third, zwitterionic surfactant systems are further reviewed, where intramolecular charge balance and distributed hydration structures contribute to enhance tolerance to high salinity, enabling more stable interfacial adsorption and more robust middle-phase microemulsion behavior. Finally, emerging concepts inspired by ionic liquid molecular design are also briefly discussed as an independent strategy for surfactant development under HSHT conditions. Overall, this review traces the evolution from conventional surfactants to salt-tolerant and zwitterionic systems, while highlighting ionic-liquid formulations as an additional pathway for microemulsion design and engineering applications under HSHT conditions. It also provides theoretical guidance for the screening and rational selection of surfactants for high-salinity reservoirs.